Westermo MA-21 User Manual

Strömslingeomvandlare

Current Loop Converter

Stromschleifenwandler

INSTALLATIONSANVISNING

INSTALLATION MANUAL

INSTALLATIONS ANLEITUNG

6021-2002

www.westermo.se

MA-21 AC

MA-21 DC

©

Westermo Teleindustri AB • 1998 • REV. A

Galvanic

Isolation

Transient

Protection

Balanced

TransmissionCEApproved

8 6021-2002

Switch settings

The MA-21 can through different switch settings be adapted to a vareity of running
conditions. To set the switches, open the plastic case by placing and turning a screw­driver between top and bottom at the rear of the case.

DANGER! DO NOT OPEN CONNECTED UNIT

12345

V.24/RS-232-C
CONNECTION

LINE

CONNECTION

MAINS

Specifications

Transmission Asynchronous, full/half duplex or simplex
Interface 1 EIA RS-232-C/CCITT V.24

25-position D-sub female, DCE

Interface 2 20 mA current loop, selectable active or passive
Data rate Up to 19.2 bit/s
Indicators Power, RD, TD
Isolation Galvanic isolation with opto-coupler (data transmission)

and transformer (supply)

Isolation voltage 1500V
Overvoltage protection Mains: Breakdown voltage 440V at 230V AC

and 220V at 115V AC
Interface 2: Breakdown voltage transmitter
and receiver 37V
Surge capacity 0.6 kW for 1ms

Power supply Switchable 115/230V +15/ –10% 48–62Hz
Fuse 100mA fast 5x20 mm
Power consumption Max 5VA at 230V AC
Temperature range 5–50°C, ambient temperature
Humidity 0–95% RH, non-condensing
Dimensions WxHxD 161x53x139 mm
Weight 0.5 kg
Mounting With rubber pads or screws. Screws: remove

the two "keyholes" on the bottom of the case

96021-2002

ON
OFF

S4

1 - 6

ON
OFF

S5 S1

1 - 91 - 6 1 - 4

S2S3

S1 Selection of transmitted signal, selection

of signal controlling CTS

S2 Selection of transmitter/receiver

normal or inverted
S3 Selection of receiver active/passive
S4 Selection of transmitter active/passive
S5 Selection of power supply

115/230V AC

Receiver active/passive

Factory settings

S3

S3

ON

123456

ON

123456

Transmitter active/passive

Passive

S4

Active

S4

ON

123456

ON

123456

Passive

Transmitted signal

Active

ON

123456789

TD

S1

ON

123456789

S1

ON

123456789

AUX

S1

ON

123456789

SRS

S1

ON

123456789

DTR

S1

CTS controlled by

ON

123456789

RTS

S1

ON

123456789

RD

S1

ON

123456789

Always high

S1

Inverted Transmitter/Receiver

Transmitter

Normal Normal

Normal

Inverted

Inverted

Inverted

Normal

Inverted

Receiver

S2

S2

S2

S2

ON

1234

ON

1234

ON

1234

ON

1234

S2

ON

1234

S3

ON

123456

S4

ON

123456

10 6021-2002

Cable

42pF/m

0.3mm

2

1200

5000m

600

6000m

2400

4000m

4800

3000m

9600

500m

19200

200m

I 2 103 TD/Transmitted Data

O 3 104 RD/Received Data

I 4 105 RTS/Request To Send
O 5 106 CTS/Clear To Send
O 6 107 DSR/Data Set Ready

– 7 102 SG/Signal Ground

O 8 109 DCD/Data Carrier Detect

I 11 – AUX/Auxiliary

I 19 120 SRS/Secondary Request to Send

I 20 108/2 DTR/Data Terminal Ready

Receiver 1 R+
Receiver 2 R­Transmitter 3 T+
Transmitter 4 T-

5 Shield

No.

1) I= Input O= Output on MA-21

Direction

Description

Description

Direction 1)

Pin
no.

CCITT V.24

Circuit no.

Connections

Line connection

(5-position screw-terminal)

Terminal connection (DCE)
(RS-232-C/V.24, 25-position D-sub, female)

5

Line connection

Transmitter

Receiver

Receiver

Transmitter

Shield 1)

4

3

2

1

R+
R­T+
T-

T+
T­R+
R-

MA-21

Twisted pairs

20mA current loop

equipment

1) If shielded cable is used, connect the shield only at one end to avoid ground currents.

Transmission range (interface 2)

Transmission rate bit/s

116021-2002

1 – Voltage
2 + Voltage
3

MA-21 DC

Specifications
Power supply 12–36V DC
Power consumption Max 3W
Insulation 1000V
Fuse F1 1.6 A fast 5x20 mm

All other specifications according to MA-21 AC

Switch settings

According to MA-21 AC

Connections

According to MA-21 AC, except power supply

Connection

no.

Power
Supply

12345

V.24/RS-232-C
CONNECTION

LINE

CONNECTION

123

POWER

12-36VDC

12 6021-2002

Hints

The 20mA current loop interface, or TTY as it is sometimes known, is a popular
industrial communications standard. The system relies on a current generator running
on both the transmit and receive circuits. On each circuit it is important to have only
one current generator supplying current into that circuit. For this reason the MA-21
can have it’s current generators set to be either active or passive. It is important to
check the state of all attached equipment to ensure correct setting on the MA-21.
The MA-21 has the same line interface as MD-21, MD-29 and are hence compatible.

The RS-232 interface is configured as DCE (Data Communication Equipment). Most
printers, PC’s and terminals are set as DTE (Data Terminal Equipment). Some recomen­dation of cable configurations are given below.

If any problems do occur on set up of theMA-21, the LED’s will be helpful.

• PWR: The unit has power.

• RD: Data received on line interface.

• TD: Data received on RS-232 interface.
A good way to check the MA-21 is to carry out a loop back test. Ensure that either the

transmitter or receiver are set to active, but not both active or passive. Connect T+ to
R+ and T- to R-. Connect the RS-232 port to a terminal. When keys are pressed on the
terminal you should receive the echo on screen. The TD & RD lights will both flicker
simultaneously as you press the keys.

1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

1
2
3
4
5
6
7
8
9

1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

DTE MA-21 DTE MA-21 9-pos. PC MA-21

136021-2002

Connecting the MA-21 in a current loop

4
3

43

RD

21

2
1

43 21

TD TD

TD

S1: 1, 5, 7, 8 on
S2: 1, 3 on
S3: 3–6 on
S4: 3–6 on

S1: 1, 5, 7, 8 on
S2: 1, 3 on
S3: 1, 2 on
S4: 1, 2 on

RD

RD

Functional description

The TD led flashes on the master when transmitting from it. The RD led flashes
on the slaves. When transmitting from a slave the TD led flashes only on that unit.
The RD led flashes only on the master modem.

Functional description

When transmitting from the master, RD and TD flash. RD flashes on the slaves.
When transmitting from a slave both RD and TD flash. On the other slaves and the
master RD flashes.

Full duplex transmission

4
3

43

RD

21

2
1

43 21

TD

Slave Slave

SlaveSlave

TD

TD

S1: 1, 5, 7, 8 on
S2: 1, 3 on
S3: 1, 2 on
S4: 3–6 on

S1: 1, 5, 7, 8 on
S2: 1, 3 on
S3: 1, 2 on
S4: 1, 2 on

RD

RD

Half duplex transmission

Westermo Teleindustri AB • S-640 40 Stora Sundby, Sweden

Phone [phone] Fax [phone]

E-mail: [e-mail] • Westermo Web site: www.westermo.se

Westermo Teleindustri AB have distributors in several countries,

contact us for further information.

Westermo Data Communications GmbH
Bruchsaler Straße 18, 68753 Waghäusel
Tel.: [phone] • Fax.:[phone]
E-Mail: [e-mail]

Westermo Data Communications Ltd
Solent Business Centre • Millbrook Road West
Millbrook, Southampton • SO15 0HW
Phone: [phone] • Fax.:[phone]
E-Mail: [e-mail]

Subsidiaries

V.24/RS-232

PE

SG

Line

T+

T-

TD

AUX

SRS
DTR

DSR
DCD

PG

Power

Supply

R+

R-

CTS

RTS

RD

Shield

7

0V

+12V

6
8

3
420

19

1
211

2

TD

2)

S1

3

S2

R51

R47

+24VB

0V

0VB

+12V

-12V

Isolated power supply

F1

1

+12V

1
2

0VB

1
4
2
5

6

3

4

20mA

+24VB

R49

PE

1

0VB

1

4
2
5
6

3

2

20mA

+24VB

R50

PE

R48

PE

S4

RD

3
4

S2

8
74

5

9

S1

6
5

3

1)

1)

1)

1)

+12V

PWR

5

0VB

S3

Block diagram

1) 0 Ω resistors R48-R51 are normally not mounted.

2) Metal housing on D-sub is connected to PE